This invention relates to circuitry for converting analog signals to and from digital form, and, more particularly, to circuitry for facilitating such conversion at relatively high speed such as for use in digital signal processing systems.
In the conversion of analog signals to digital form such as particularly when the data is in serial form, there are time delays associated with clocking the data into and out of devices such as holding registers and the like. In digital processing systems in which analog data must be converted to a digital format before and after digital processing, the delays associated with conversion between serial and parallel formats degrade overall system performance by resulting in an undesirably long total processing interval. For example, an analog-to-digital (A/D) conversion of the signal to be processed must first occur. An appropriate interval for such conversion must be allocated during the processing cycle. A further delay is then utilized for transferring data serially into the digital processor circuitry. After processing, the data must then be transferred into a digital-to-analog (D/A) converter for conversion to the analog form for further processing or other purposes.
Accordingly, it is desired in such processing systems to minimize the conversion time as well as the associated data clocking intervals, data transmitting intervals, and other necessary delays and to achieve a minimum overall cycle period, whereby the overall processing time will be shortened, leading to greater processing bandwidth and capacity.
There have been proposed heretofore various high speed conversion schemes. Thus, for example, it is possible to utilize various exotic conversion techniques including so-called flash converters. Another possibility is the conversion of input data into parallel data streams with simultaneous parallel signal processing of the several streams. However, all such schemes having suffered from complexity and high cost, do not permit widespread commercial usage where simplicity and economy are needed. Further, if a single microprocessor is to be utilized for implementing a digital signal processing algorithm, data input must be provided.
Accordingly, among the several objects of the invention may be noted the provisions of improved analog-digital conversion system; the provision of such a system which includes improved A/D as well as D/A conversion; which minimizes processing intervals associated with A/D conversion; which allows overlapped A/D and D/A conversion coupled with processing greatly minimizing overall cycle times associated with such conversion; and which, when utilized with a digital signal processing system, brings about overall cycle times of markedly reduced interval for enhancing processing rates and increasing bandwidth; which provides for increased Nyquist frequency of analog-digital conversion; and which eliminates wasted or excessive "wait" periods during operation of the system and processing circuitry which may be utilized with the conversion system.
It is further an object of the invention to provide an analog-digital conversion system providing an increased speed of conversion of analog input signals to a serial digital data stream for digital processing of such data by use of a microprocessor for implementing a digital signal processing algorithm to provide real-time processing of the datastream, and for providing rapid accurate conversion of the processed digital signal into an analog output signal for further use.
It is a further object of the invention to provide such a conversion system which is simply and economically configured thereby to permit widespread commercial adoption of the system, including direct incorporation of the system as in the form of a large scale integrated circuit (LSI) device into various types of commercial and consumer equipment such as microphones, amplifiers, radio receivers, modulators, modulator-demodulators (modems), transmitters and transceivers, and portable or hand-held units; and which may be incorporated into other integrated circuit devices.
It is also an object of the invention to provide such a conversion system which can be used for conversion of various kinds and forms of analog signals into digital format for further processing with or without further conversion of the processed signals into analog or other formats.
Other objects and aspects of the invention will be apparent or are set forth below.